To realize the white light emitting from blue light emitting by converting a wavelength from a nitride semiconductor light emitting device, a device of combination with a gallium nitride light emitting device and YAG:Ce phosphor is proposed. The mechanism for obtaining the white light from emitting device of converting a wavelength generally comprises steps of mixing phosphor powder into coating of LED chip or mold resin, absorbing a part of the emitted light from the chip into the phosphor, exciting a phosphor, mixing the excited light from the phosphor with the emitted light from the chip which is not absorbed, and forming a mixed colored light.
However, the method for manufacturing the phosphor layer using the phosphor mixed with the coating or mold resin has some problems: the degree of dispersion of the phosphor in the resin is varied by descending the phosphor during a process of solidifying the resin, uniform mixed color cannot be obtained, and the yield is very low.
To overcome aforementioned problems, it was attempted that the gallium nitride semiconductor layer was formed directly on the substrate obtained by YAG single crystal to obtain a uniform phosphor layer, but it was found that it was difficult to carry out the vapor phase growth of the gallium nitride crystal on the YAG crystal through the buffer layer.